Alteration of the carbon and nitrogen isotopic composition in the Martian surface rocks due to cosmic ray exposure

C-13/C-12 and N-15/N-14 isotopic ratios are pivotal for our understanding of the Martian carbon cycle, history of the Martian atmospheric escape, and origin of the organic compounds on Mars. Here we demonstrate that the carbon and nitrogen isotopic composition of the surface rocks on Mars can be sig...

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Bibliographic Details
Published in:Journal of geophysical research. Planets 2014-06, Vol.119 (6), p.1390-1402
Main Authors: Pavlov, A. A., Pavlov, A. K., Ostryakov, V. M., Vasilyev, G. I., Mahaffy, P., Steele, A.
Format: Article
Language:English
Subjects:
Carbon
Carbon 12
Carbon content
Carbon cycle
carbon isotopes
Chemical composition
Cosmic ray showers
Cosmic rays
Exposure
Galactic cosmic rays
High temperature
Isotope composition
Isotope ratios
Isotopes
Lunar And Planetary Science And Exploration
Mars
Mars atmosphere
Mars surface
Meteors & meteorites
Nitrogen
Nitrogen isotopes
Nuclear reactions
Organic compounds
Oxygen
Oxygen atoms
Rocks
SNC meteorites
Solar cosmic rays
Spallation
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Summary:C-13/C-12 and N-15/N-14 isotopic ratios are pivotal for our understanding of the Martian carbon cycle, history of the Martian atmospheric escape, and origin of the organic compounds on Mars. Here we demonstrate that the carbon and nitrogen isotopic composition of the surface rocks on Mars can be significantly altered by the continuous exposure of Martian surface to cosmic rays. Cosmic rays can effectively produce C-13 and N-15 isotopes via spallation nuclear reactions on oxygen atoms in various Martian rocks. We calculate that in the top meter of the Martian rocks, the rates of production of both C-13 and N-15 due to galactic cosmic rays (GCRs) exposure can vary within 1.5-6 atoms/cm3/s depending on rocks' depth and chemical composition. We also find that the average solar cosmic rays can produce carbon and nitrogen isotopes at a rate comparable to GCRs in the top 5-10 cm of the Martian rocks. We demonstrate that if the total carbon content in a surface Martian rock is
ISSN:2169-9097
2169-9100
DOI:10.1002/2014JE004615